Eubria mesoamericana Barr and Shepard, 2017

Barr, Cheryl B. & Shepard, William D., 2017, Eubria mesoamericana Barr and Shepard (Coleoptera: Psephenidae: Eubriinae), a New Psephenid Species from Central America with an Enigmatic Generic Distribution, The Coleopterists Bulletin 71 (3), pp. 437-444 : 438-443

Eubria mesoamericana Barr and Shepard , new species

( Figs. 1–4 )

Type Material. HOLOTYPE ♂ in USNM, labeled “ PANAMA, Cocle, / El Valle, 829m / 27 May 1983 // Collected by / P. J. Spangler ” // [genitalia vial] // “♂ tail to YTS [Young T. Sohn] / to draw #253 / in spot plate // HOLOTYPE / Eubria / mesoamericana / Barr & Shepard” [red label, handwritten]. Eight paratypes [yellow labels, printed] were examined from the following localities: PANAMA: Cocle, / El Valle, 829m / 27 May 1983 // Collected by / P. J. Spangler (1♂, USNM); Colón Prov. / Rio Guanche / 5 km S Portobelo / 09°30.202’N 79°39.903’W / 18-vii-1999, el. 100 ft. / J. B. Woolley, 99/031 (1♂, TAMU); Veraguas / Prov., Que. de Venado / ~ 4 km S Las Palmas / 27- VIII-2006, C. B. Barr // 08°05.987’ N / 81°26.076’ W / elevation 729 ft. // [genitalia vial] (1♂, EMEC); Barro Colo [rado] Is [land] / C[anal] Z[one] Mar Apr 49 / Zetek 5393 //? Eubrianax / n. sp. / HSB 49 (1♂, USNM); Paraiso C[anal]Z[one] / Pan [ama] I.20.11 / August Busck // Ectopria / n. sp. (1♀, USNM); PortoBello / Pan [ama] Mar 1911 / August Busck (1♂, USNM). COSTA RICA. Prov. Limón, R.B. / Hitoy Cerere , Sendero Toma de Agua , / 100 - 200m, 19 MAR - 2 ABR 2002, / W. Arana, Manual , / L N 184300 643450 #67803 // [barcode label] INB0003457667 / INB!OCR! COSTA RICA (1♀, MNCR); San José / Prov., sm. stream at Rta. / 243, 2 km NE Tinamaste / SW San Isidro de General / 22-VI-2001, coll. C. B. Barr // 09°18.55’ N / 83°46.05’ W / elevation ~ 2750 ft. // [genitalia vial] (1♂, EMEC).

Description. Holotype male. Length (pronotum + elytra) 1.8 mm, width 1.2 mm. Body convex, broadly ovate in dorsal view ( Fig. 1A ); cuticle brown to redbrown except for yellow-brown left elytron; covered with short, fine, recumbent, golden setae; elytra with a series of irregular, linear, granulate impressions ( Figs. 1A , 3B ). Antenna: With 11 antennomeres, together as long as body or nearly so; brown, covered with evenly distributed, short, stiff, golden setae and cup-shaped sensillae; antennomere 1 cylindrical, as long as wide; antennomere 2 wider than long, 1/2 the size of antennomere 1; antennomeres 3–8 flattened, broadly serrate, each with width at apex more than 1/2 the length; antennomeres 9–11 flattened, progressively less broadly serrate (right antenna missing antennomere 11; left antenna with antennomeres 10 and 11 glued to card point). Head: Opisthognathous ( Fig. 1B ), dark brown, with prominent antennal ridges between eyes. Eye black, prominent, hemispherical, slightly emarginate to accommodate antennal base. Clypeus tipped at 90° angle to frons; anterior border slightly arcuate; lateral surfaces at 90° angle to disc, excavated to accommodate antennae in repose. Labrum subpentagonal, lateral borders rimmed; brown basally, yellow and setose apically. Maxillary palpus pale yellow, very long, with 4 palpomeres; apical palpomere elongate with 3 processes at tip. Labial palpus pale yellow, length less than half that of maxillary palpus, with 3 palpomeres; apical palpomere globular with 3 processes at tip. Pronotum: Transverse, more than twice as wide as long, much wider at base than apex ( Fig. 1A ); length 0.4 mm, width 1.0 mm; brown, covered with numerous fine, recumbent setae; margins with low, dark carina. Anterior margin curved basad; lateral margins slightly arcuate; posterior margin slightly bisinuate, nearly straight anterior to scutellum; apicolateral angles broadly rounded; posterolateral angles more narrowly rounded. Scutellum broadly, equilaterally triangular, disc flat and slightly depressed relative to elytra, setose. Elytron: Twice as long as wide ( Fig. 1A ), length 1.4 mm, width 0.6 mm, widest at apical 1/3; broadly rounded laterally; right elytron red-brown, left elytron yellow-brown. Disc depressed adjacent to scutellum; moderately convex, with 6, mostly longitudinal, irregular, impressed lines of various lengths, some interconnected ( Figs. 1A , 3B ), containing fine granules; humerus prominent and raised, smoothly rounded; basal and lateral margins with dark carinae; epipleuron flat, bordered laterally and mesally with dark carinae extending to apex. Metathoracic wings entire. Legs: Prothoracic leg shortest, metathoracic leg longest (left metathoracic leg detached from body and glued on card point); legs of similar proportions, each with femur and tibia about the same length. Profemur yellow, protibia yellow-brown; meso- and metafemora yellow-brown, meso- and metatibiae darker; all tarsi yellow. All coxae transverse, metacoxa shortest and very narrow laterally; each coxa incised for reception of femur, posterior margins with dark carinae. All legs with each femur having posterior surface grooved for reception of tibia. Tarsi very setose; each tarsus with 5 long, cylindrical tarsomeres; tarsomeres 1–4 progressively shorter distally, tarsomere 5 longest, as long as previous 3 combined; pretarsus with 1 claw simple, 1 claw apically bifid, with long, white empodium between claws. Venter: Cuticle redbrown ( Fig. 1B ). Prosternum short, transverse; setose; hypomeron slightly convex; prosternal process narrow between procoxae, apex rounded. Mesosternum short, disc flat, posterior border truncate between metacoxae; heavily setose; episternum and epimeron triangular. Metasternum about 3 times wider than long; strongly convex; heavily setose except where abraded at center of disc; episternum quadrate. Abdomen with 5 visible, setose ventrites; ventrites 1–4 transverse, much wider than long, posterior borders smooth; ventrite 5 broadly triangular with rounded apex. Genitalia: Weakly sclerotized. Phallobase short with parameres attached at base; parameres very narrow in dorsal view ( Fig. 2A ), curved laterally outward toward apex, tip acute; flat, blade-like accessory sclerite with rounded tip between each paramere and penis; penis broad basally, becoming very narrow at middle, tip dorsally recurved and distinctly hooked ( Fig. 2B ). Accessory sclerites longer than parameres and penis; penis shorter than parameres.

Female. Eubria mesoamericana , like other eubriines, is sexually dimorphic. The antennae of the female are only slightly serrate, and the length is about half as long as that of the male. The tarsi, including the claws, are narrower, smaller, and more delicate in appearance than those of the male. Both claws of the female are simple, whereas one claw of each pair is bifid in the male. Acknowledging the small sample size, there was no difference in overall body size between males (n = 7) and females (n = 2).

Variation. The range in body size of the nine specimens examined was 1.7–1.9 mm in length and 1.2–1.5 mm in width. Body shape in dorsal view varied from round to broadly ovate, and the overall color varied from yellow-brown to red-brown. Leg color differed among specimens, with the femora ranging from yellow to yellow-brown and often darker basally, along the posterior surface, and at the apex; tibiae were yellow-brown to brown and darker than the rest of the leg. The impressed lines on the elytra are variable in number, configuration, and interconnectivity among the specimens examined ( Fig. 3 ). Most have six lines on each elytron, however, one has as few as three. The difference in color between the left and right elytron of the holotype specimen is not a normal condition, and the cause is unknown.

Diagnosis. Because of its shape and very small size, E. mesoamericana cannot be confused with any other described species of Psephenidae in the Neotropics. The species is most closely related to the Old World species E. palustris and very similar in appearance. Aside from their greatly disjunct geographic distributions, the species can be separated morphologically by the configuration of impressed lines on the elytra and by the number of apical processes on the labial palpi. In E. mesoamericana , the impressed line closest to the suture is unbroken from near the scutellum almost to the apex ( Fig. 3 ), whereas in E. palustris there are two lines near the suture, separated at about the basal third. The labial palpus of E. mesoamericana has three projections at the tip of the apical palpomere; E. palustris has four projections (Lee and Jäch 1996). In addition, the male genitalia are very different, with that of E. palustris having much broader parameres and penis than that of E. mesoamericana ( Fig. 2 ), as well as having three pairs of accessory sclerites (one pair in E. mesoamericana ). Illustrations of the elytron and genitalia of E. palustris appear in Lee and Jäch (1996).

Eubria mesoamericana differs in the following respects from the description and diagnosis of Eubria offered by Lee and Jäch (1996), therefore, these characters should henceforth be considered species characters: posterior margins of abdominal ventrites 3 and 4 are smooth rather than serrate; and the labial palpi of both sexes bear three projections on each tip rather than four ( Fig. 1B ).

Etymology. The Latin name “ mesoamericana ” refers to the geographic region of origin, Mesoamerica (i.e., Central America). The gender is female.

Eubria palustris Examined for Comparison. Slov. or. lgt. Boukal / Bukovské vrchy / NOVÁ SEDLICA / 5.7.1990 // Eubria / palustris Er. / Det. D. Boukal 1990 (1♂, EMEC); ‘60 // n. Wienerwald // Eubria / palustris ER. / det. M. Jäch 1995 (1♀ [?], EMEC).

Larval Material Examined. COSTA RICA: Alajuela / N of Bijagua 650 m / 6 VI 2000 / R´ıo Bijagua / WDS-A-1298 [on reverse] // William D. / Shepard, leg. (2, EMEC) ; Alajuela / SE of Bijagua / 7 VI 2000 / R´ıo Flores / WDS-A-1300 [on reverse] // William D. / Shepard leg. (1, EMEC) ; Cartago / 4 km N Pavones / 23 XI 2002 / R´ıo Chitaria / WDS- A-1494 [on reverse] // William D. / Shepard, leg. (1partial exuvium, EMEC) ; Guanacaste / Rincón de la Vieja / Lodge 19 ̛ I ̛ 2000 / R´ıo Colorado / WDS- A-1287 [on reverse] // William D. / Shepard, leg. (1, EMEC) ; Puntarenas / NE of Dominical / 19 VI 2000 200 m / unnamed stream / WDS-A-1315 [on reverse] // William D. / Shepard, leg. (1 exuvium, EMEC) .

Larval Description. General description based on four individuals. Length 2.3–3.5 mm. Body ( Fig. 4 ) depressed, round to broadly ovate depending on amount of contraction, lateral margins explanate. Dorsum yellow-brown with darker brown mottling on tergites, paratergites (pleural processes) yellow. Dorsum ( Fig. 4A ) with brown tubercles arranged in irregular longitudinal lines; thorax with moderately dense, scattered tubercles laterad of longitudinal lines. Paratergites with dense fringe of long, white, transparent setae on all margins. Prothorax without mid-dorsal longitudinal sclerite; median ecdysial suture complete; 1 row of brown tubercles on each side of ecdysial suture. Mesothorax, metathorax, and abdominal segments I–VIII with 3 rows of brown tubercles on each side of midline, forming 2 lateral pairs of irregular lines and paler central pair with mid-dorsal suture between; abdominal segment IX with only 4 rows total.Abdominal segments I–VII with paratergites becoming successively longer, more curved, and with apices more acutely angled towards apex; 7 th paratergites longest, extending posteriorly to tip of 8 th paratergites and enclosing them laterally. Eighth paratergites short, extending only to mid-length of abdominal segment IX, rounded apically, with reduced setal fringe. Abdominal segment IX wider than long; anterior border straight, lateral borders slightly concave to receive 8 th paratergites; posterior border broadly rounded and densely setose. Venter ( Fig. 4B ) white, membranous except for paratergites, legs, and well-sclerotized tips of tarsunguli. Ventral operculum present on segment IX, concealing gills beneath.

Larval Diagnosis. The larva of E. mesoamericana closely resembles that of E. palustris , which is illustrated in Bertrand (1954) and Lee et al. (2016) as Eubria . Although larvae generally can be distinguished only to the generic level, apparent slight differences between the two species include the wider first abdominal paratergite and shorter, less semicircular apex of the ninth abdominal segment of E. mesoamericana ( Fig. 4 ). The only other Neotropical larvae without external gills, with which E. mesoamericana may be confused, are those of Dicranopselaphus Guérin-Méneville and Neoeubria Shepard and Barr. Unlike Eubria , Dicranopselaphus larvae have long, narrow, strongly hooked paratergites on all segments from the prothorax posteriorly to abdominal segment VII, and abdominal segment IX is elongate and deeply notched at the apex. Neoeubria larvae have broadly rounded paratergites, and abdominal segment IX is large and semicircular. In addition, there are four pronounced, longitudinal ridges on the dorsum of Neoeubria . Illustrations of several Old and New World eubriine larvae are found in Lee et al. (2007).

Habitat and Associated Aquatic Byrrhoids. We swept two E. mesoamericana adults from riparian vegetation at a small and a medium-sized stream, both with shallow, clear water and substrates of sand, gravel and cobble ( Fig. 5 ). Label data from five adult specimens, including our two, show an elevational range of 31– 829 m. Larvae, collected by us from five localities with elevations ranging 200–844 m, were from medium-sized streams with sandy/gravelly substrates that contained woody debris and leaves.

Other aquatic byrrhoid Coleoptera collected in conjunction with E. mesoamericana larvae included the following: Dryopidae - Dryops mexicanus (Sharp) , Elmoparnus pandus Spangler and Perkins ; Elmidae - Austrolimnius sp. , Cylloepus sp. , Disersus longipennis Sharp , Disersus uncus Spangler and Santiago , Heterelmis sp. , Hexacylloepus sp. , Hexanchorus gracilipes Sharp , Hexanchorus usitatus Spangler and Santiago-Fragoso , Microcylloepus sp. , Neoelmis sp. , Notelmis nodipes (Sharp) , Phanocerus clavicornis Sharp , Phanocerus congener Grouvelle , Pseudodisersus goudotii (Guérin-Méneville) , Xenelmis bufo (Sharp) ; Lutrochidae - Lutrochus sp. ; Psephenidae - Psephenops maculicollis Darlington , Psephenus sp. ; Ptilodactylidae - Anchytarsus palpalis (Champion) . In general, most of the streams with E. mesoamericana larvae were typified by a high diversity of aquatic byrrhoids.

Distribution. At present, E. mesoamericana is known from 13 locations in Costa Rica (seven) and Panama (six). Within these countries, the known distribution is very patchy, and the species is possibly rare, or at least uncommonly collected.

Figures

Fig. 1. Eubria mesoamericana, adult males (length = pronotum + elytra). A) Dorsal view, length 1.7 mm, B) Ventral view, length 1.8 mm.

Fig. 2. Eubria mesoamericana, holotype, male genitalia. A) Ventral view, B) Lateral view.

Fig. 3. Eubria mesoamericana, elytral variation. A) Female from Limón Province, Costa Rica, B) Holotype male from Coclé Province, Panama, C) Male from Colón Province, Panama.

Fig. 4. Eubria mesoamericana, larva. A) Dorsal view, B) Ventral view.

Fig. 5. Eubria mesoamericana, adult collection site in San José Province, Costa Rica.